It said it was ready to help UK musicians and the wider industry "maximise the opportunities ahead."

Mr Hughes, who founded the Welsh Proms, said it was "vitally important to alleviate this uncertainty" for musicians from EU countries who play for UK orchestras.

"We don't know what's going to happen to them. Are they going to be uncertain and choose to leave the orchestra and go home, so everybody leaves the orchestra?" he said.

"There's the uncertainty of, 'Do we stay, what is going to happen?"

Mr Hughes regularly conducts orchestras in Cardiff and London and carries out engagements in European cities.

He said it was currently straightforward to bring singers or musicians from EU countries as last-minute replacements for performances in the UK, but restrictions on movement could impact future concerts.

"Let's say there's an opera going on in Covent Garden and the singer goes ill, as often happens. Normally you can get somebody like that who can come from anywhere.

"But if that freedom goes, you'll never get anyone in time. They'll be going through visa applications and goodness knows what.

"Same thing with instrumentalists playing concertos and so on, to have that freedom knowing the role can be filled by anybody is very, very important."

Regard it as an opportunity rather than a threat

Mike Smith, arts journalist

Arts journalist Mike Smith, who supported the campaign to leave the EU, said: "My main message to them is to regard it as an opportunity rather than a threat.

"To look at the things we have learnt from the European Union - that we do need access for artists to be able to travel across borders, but we should go back to a more internationalist view, and that actually we should be negotiating for free access on the global stage."

Artists and their instruments currently enjoy relatively free movement between EU countries.

Outside the EU, performers and their equipment must often pay for visas and other documentation.

Andy Farquharson is a logistics manager responsible for organising orchestral tours and concerts.

He said: "At the moment it's relatively simple, certainly within the EU. If you want to go further afield it does require more licences not just for the performers themselves, but actually for their instruments as well. They are classed as cultural goods.

"So at the moment it is relatively free to move those around, but I think the concern is that if those borders come closer to home then actually the movement is going to become more tricky.

"And that's where companies such as mine will be more heavily involved in supporting people because when you go to actually move and run the tour it's a bit too late if you haven't got the paperwork in place. So yeah, it could potentially be quite tricky."

Welsh folk group Calan tours extensively in the EU and around the world.

Violinist Angharad Jenkins said: "At the moment, going to Europe is very easy. All you have to do is book your flight and you are there - you could take a gig this weekend and you wouldn't have to think twice about it.

"America, on the other hand, there's a huge logistical problem to overcome in that you have to get working visas to go over there."

She said plans to tour the EU after March 2019 would be formalised next year.

"We tend to work about 18 months in advance, we know what we are doing until the end of 2018. But of course next year we will be starting to plan what's happening in 2019 and my hope is that it will continue to be the same and that we can move freely around Europe, but who knows?"

The Department for Exiting the European Union said: "We are working across UK Government to identify and develop options to shape our future immigration system.

"We are engaging with businesses and communities through a series of Brexit roundtables to understand the opportunities and challenges that arise from our EU exit including touring musicians and crews.

"We want music in all its forms to continue to thrive and stand ready to help UK musicians and the wider industry maximise the opportunities ahead."